Subject: [BEHAVE] DSCP and TURN

From: Brian E Carpenter <[email-masked]>
Date: Mon, 23 Jun 2008 09:21:41 +1200

Hi,

I've looked at section 11.1 "DiffServ Code Point (DSCP)"
in draft-ietf-behave-turn-07.txt.

I believe that what it says is correct (and consistent
with general recommendations for handling DSCPs in any
form of packet munging device). However, you could add
something like this:

If the TURN server is immediately adjacent to a differentiated
services classifier [RFC2474], then DSCP copying MAY be omitted
in the direction towards the classifier.

(If you imagine a device that contained TURN and a diffserv
classifier in one box, it would be quite pointless for the TURN code
to copy DSCP values that the classifier was about to modify.)

    Brian

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From: Philip Matthews <[email-masked]>
Date: Tue, 24 Jun 2008 11:40:27 -0400

Brian:

Section 11 has been totally rewritten in the upcoming TURN-08  
revision. The new text allows the server to set the DSCP to some other  
value if it believes, through configuration or other means, that a  
different setting is more appropriate. I think this covers the  
situation you describe below.

- Philip

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From: Brian E Carpenter <[email-masked]>
Date: Wed, 25 Jun 2008 09:26:10 +1200

Philip,

On 2008-06-25 03:40, Philip Matthews wrote:
> Brian:
> 
> Section 11 has been totally rewritten in the upcoming TURN-08 revision.
> The new text allows the server to set the DSCP to some other value if it
> believes, through configuration or other means, that a different setting
> is more appropriate. I think this covers the situation you describe below.

Well sort of, but I think it fudges the diffserv architecture slightly.
Diffserv doesn't operate on "belief". In fact, the only case
where what you describe is inappropriate is when there is
a diffserv classifier in the neighbourhood. So may I suggest:

   Diff-Serv Code Point

      Preferred Behavior: Set the outgoing value to the incoming value,
      unless the server includes a differentiated services classifier
      and marker [RFC2474].

      Alternate Behavior: Set the outgoing value to a fixed value,
      which by default is Best Effort unless configured otherwise.

      In both cases, if the server is immediately adjacent to a differentiated
      services classifier and marker, then DSCP setting MAY be omitted
      in the direction towards the classifier.

        Brian

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From: Philip Matthews <[email-masked]>
Date: Wed, 25 Jun 2008 06:46:24 -0400

On Tue, 24-Jun-08, at 17:26 , Brian E Carpenter wrote:
>> revision.

Brian:

I have adopted your text with one change. For the third paragraph, I  
have used:

      In both cases, if the server is immediately adjacent to a  
differentiated
      services classifier and marker, then DSCP MAY be set to any  
arbitrary value
      in the direction towards the classifier.

I think this more accurately captures what you mean by "omitted".

- Philip

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From: Brian E Carpenter <[email-masked]>
Date: Thu, 26 Jun 2008 09:47:46 +1200

> I think this more accurately captures what you mean by "omitted".

Sure

    Brian